﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace digui
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(Cheng(31));
            Console.ReadKey();
           
        }

        static int Cheng(int num)
        {
            if (num-1!=0)
            {
                return Cheng(num - 1) * num;
            }
            return 1;
        }
    }
}
